Imperfect thread removal tool

ABSTRACT

Disclosed herein is an apparatus for removing the imperfect, runout threads in large diameter, internally threaded stud holes. The apparatus comprises a tool-holder assembly provided for automatically locating the thread-grinding tool with respect to the thread to be operated on and means for accurately guiding the tool along a helical path corresponding to that of that thread upon rotation of the tool holder.

0 M :1 Wm. J H 11 it States t Conner [54] IMPERFECT THREA REMOVAL 1,068,861 7/1913 Dersch ..s1/241 B TOUL 1,857,873 5/1932 Ross ..5 1/241 B Inventor: James M Conner Chattanooga, Tenn 2,465,599 3/1949 McDiarmld ..5l/24l B [73] Assignee: Combustion Engineering, llnc., Windsor, Primary Examiner-William R. Armstrong Conn. AttorneyCarlton F. Bryant, Eldon H. Luther, Robert L. 01- 2 Fl d: 2 son, John F Carney, Richard H. Berneike, Edward L. Kochey, 2] i e July 1970 Jr and Lawrence P. Kessler [21] Appl. No.: 57,659

[57] ABSTRACT 1 I 1/241 3, 51/24 A Disclosed herein is an apparatus for remon'ng the imperfect. I'll. CL... t v un ut thread large diameter internally threaded stud |58| Held of Search ..51/32, 90, 241 B, 241 S, 241 VS, holes The apparatus comprises a mopholder assembly 51/24 241 245 vided for automatically locating the thread-grinding tool with Reierences Cited respect to the thread to be operated on and means for accu- UNITED STATES PATENTS 7/1912 Hunter ..5l/241B rately guiding the tool along a helical path corresponding to that of that thread upon rotation of the tool holder.

4 Claims, 9 Drawing Figures mimanmwmz 3.634.981

SHEET [BF 2 INVENTOR. J'AMEs M CON V52 A TTOENEY BACKGROUND OF THE INVENTION In the manufacture of high-pressure vessels, such as those embodied in nuclear power plants, large diameter studs are provided about the circumference of the vessel flange for securing the closure head. The holes drilled in the flange for reception of the studs contain an internal thread. It is found that in machining these threads imperfections in the form of burrs and rough edges are prone to occur especially at the leading and trailing edges of the thread. In these instances it is sometimes necessary to grind the thread down to its root diameter thus to completely eliminate the thread over a limited portion of its length, as for example, a half turn or more.

In order to eliminate the imperfections in the past, elimination of the imperfections has been accomplished by manually guiding an electric-motor-driven deburring tool along the effected portion of the thread repeatedly until the roughened thread has been eliminated. Such procedure obviously suffers from the disadvantage that it is both tedious and time consuming. Additionally, by means of this procedure there is always presented the danger of damage to the adjacent thread that would be caused by an errant application of the tool.

It is to the avoidance of the above-mentioned problems therefore that the present invention is directed.

SUMMARY OF THE INVENTION According to the present invention an apparatus in the form of a holder or a deburring tool is provided which enables the tool to be accurately centered within an internally threaded hole and which permits a workman to quickly and easily manipulate the tool along the thread to be worked without danger of damaging any of the adjacent threads. The tool holder comprises a shaft to one end of which the deburring tool is mounted in a manner that permits its radial adjustment. The shaft at its other end is fixedly mounted within a plug nut bearing external threads that enables its engagement with the thread to be worked. Means are provided for rotating the entire assembly about the axis of the hole whereby the orbit of the tool will be such as to accurately conform to the helix of the thread being worked.

A principle object of the invention, therefore, is the provision of means for efficiently removing burrs or other imperfections from the internal threads of an enlarged stud hole, or the like.

Another object of the invention is the provision of means for accurately centering a deburring tool on the axis of a thread to be worked and for insuring its objective movement along a helical path conforming to that of the thread.

A still further object of the invention is the provision of means for operating a deburring tool along a thread to be worked in a manner that avoids the danger of damaging threads adjacent that being operated on.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is an elevational view, partly in section, of apparatus constructed according to the present invention;

FIG. 2 is a plan view of the apparatus shown in FIG. 1;

FIG. 3 is a partial sectional view taken along line 33 of FIG. 2;

FIG. 4 is an elevational view illustrating a mounting shaft as employed in the present invention;

FIG. 5 is an end view of the mounting shaft shown in FIG. 4;

FIG. 6 is a partial view taken along line 6-6 of FIG. 4;

FIG. 7 is a plan view ofa slide plate employed in the present invention;

FIG 8 is a side view of the slide plate of FIG. 7; and

FIG. 9 is a plan view of the lock plate employed in the present invention.

2 DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings the numeral 10 indicates a work member having, at 12, an aperture bearing an internal thread 14. More particularly, the work member 10 can be taken to be the flange of a large diameter vessel containing high-pressure fluid with the aperture 12 being intended to receive threaded studs (not shown) for connection of a closure head.

In the fabrication of such work members it commonly happens that the last turn or portion of a turn of the internal threads 14 contains roughened surfaces or burrs or is otherwise imperfectly formed. It is to expeditiously remove this im perfectlyfonned thread that the present novel apparatus, indicated generally as 20, is provided. The apparatus 20, in the form of a tool holder, is arranged to attach a grinding tool 21, illustrated in phantom in FIG. I and comprising a rotating grinding head 22 and an electrically operated drive motor 24.

The apparatus 20 comprises a generally cylindrical plug base 26 having external threads 28 for engagement with the internal threads 14 of the work member 10. The plug base 26 is provided with an axial through opening 30 containing a flanged bushing 32 for reception of a mounting shaft 34 that is, at its closure end, fixedly secured to the plug base and which carries, at its upper end, a radially adjusted tool support frame 36.

The mounting shaft 34, which is shown in detail in FIGS. 4, 5 and 6, if of composite shape having at its lower end, shown in the left in FIG. 4, a reduced diameter portion 38 containing external threads for reception of locknuts 40 and washer 42. Adjacent the thread portion 38 is a smooth cylindrical portion 44 having an axial length substantially equal to that of the bore of bushing 32 and of a diameter for a sliding fit within the bore. Next is an externally threaded portion 46 of somewhat greater diameter than that of the cylindrical portion 44 thereby forming an annular shoulder 48 for seating on the uppermost portion 50 of the plug base 26. The threads of portion 46 are adapted to receive clamp nut 52 whose function it is to securely fasten the shaft 34 to the plug base 26.

Although any of several forms of locknuts may be employed to secure the shaft 34, the clamp nut 52 shown in the drawings is one whose body at its lower end contains an enlarged diameter bore portion 54 that is axially spaced from the internal threads 56. The external surface of the nut 52, at its lower end, is conically formed as at 58 to provide a camming action that renders the nut body somewhat deformable when drawn down upon the upper surface of the plug base 26 thereby to effect binding engagement between the threads 56 and those of the shaft portion indicated as 46. The clamp nut 52 may be adapted to receive an operating rod 60 as shown in FIG. 2 to facilitate rotation of the member into and out of locked relation in the assembly.

Above the threaded portion 46, the mounting shaft 34 is, at 62, formed of a rectangular cross section for mounting the tool support frame 36. A transition section such as indicated at 64 may be employed for connecting the two portions. It should also be noted that, as in the disclosed arrangement, portion 62 may be disposed in slightly offset relation to the axis of the lower, cylindrical portion of the shaft in order to provide additional diametral space within which to accommodate the tool 21. At its upper end the portion 62 is provided with a section 66 formed of reduced width to provide shoulders 68 for seating the tool support frame 36. Atop this section is provided a cylindrical centering boss 70 containing an internal threaded bore 72 for locating and attaching by means of connector 73 the slide plate 74 and clamp plate 76 that serve to connect the frame to the shaft as hereinafter described.

The tool support frame 36 is described with particular reference to FIGS. 1, 2 and 3. As shown, it is formed in two sections, a main section 78 and a clamping section 80 that is attached to the main section by fasteners 82, The main section 78 of the toolsupport frame is of composite shape having an external semicylindrical recess 84 that cooperates with a similar recess 86 in the clamping section 80 for reception of the tool 21. An elongated slot 88 opens into the recess 84 and is sized for sliding engagement with the side surfaces of the reduced width section 66 of the rectangular shaft portion 62 upon the shoulders 68. As shown best in FIG. 3 the side surfaces of the slot 88 are stepped adjacent the upper surface of the frame to form a pair of shoulders 90 and 92, the former to engage the slide plate 74 and the latter to engage the clamp plate 76.

Means are provided for adjusting the position of the total support frame 36 radially with respect to the axis of the mounting shaft 34. These include an externally threaded rod 94 having an enlarged circular head 96 at one end and means at the other end for attaching an operating hand wheel 98. The rod 94 is, as shown, caused to pass through an internally threaded aperture 100 disposed at one end of the main frame section 78 on the longitudinal axis thereof and opening at its inner end to the slot 88. When assembled, the head 96 of the rod 94 is lodged, but free to rotate, in a radially undercut recess 102 provided in the section 66 of the mounting shaft 34. Due to the mutual engagement between the threads on the rod 94 and those in the aperture 98 rotation of the rod will effect linear movement of the tool-support frame 36 with respect to the axis of shaft 34 thereby to permit radial adjust ment of the grinding head 22 of tool 21 with respect to the threads 14 to be worked.

The operation of the disclosed apparatus is as follows. To remove the imperfect end of an internal thread that has been cut in an enlarged diameter aperture as, for example, in the stud hole of a pressure vessel flange an appropriate plug base 26 (that is, one having an external thread 28 that corresponds to the thread 14 of the workpiece) is first selected. Thereafter, the apparatus is assembled as shown in FIG. 1 with the mounting shaft 34 secured to the selected plug base 26 and the tool-support frame 36 in seated engagement upon the shouldered upper end of the shaft and attached thereto by means of the threaded connector 73 and clamp plates 76. The grinding tool 21 can be clamped to the frame 36 either before or after assembly of the apparatus 20 to the workpiece 10 which step is effected by simply engaging the threads 28 of the plug base 26 with those of the workpiece. The assembly is then rotated within the workpiece an amount to dispose the grinding head 22 of the tool 21 in alignment with the end portion of the thread 14. Hand wheel 98 is next rotated to place the grinding head 22 in its operative position with respect to the thread. The tool 21 can be placed in operation either before or after the toolhead 22 is placed in position with the thread. Thereafter, the entire assembly is caused to be rotated within the aperture 12.

Because the axial position of the grinding head 22 is fixed with respect to the plug base 26 and because the plug base is in threaded engagement with thread 14 being worked by simply rotating the entire assembly within the aperture 12 the grinding head will be caused to accurately follow the thread. As the assembly is rotated within the aperture 12 the handwheel 98 is turned to feed the toolhead 22 radially into the thread such that that portion of the end containing burrs or other imperfections can be removed down to the thread root. Normally, the last half or three-quarter turn of thread is removed and this is accomplished by repeatedly rotating the assembled apparatus over the affected thread while feeding the grinding tool into the thread prior to each pass. The procedure is continued until the effected portion of thread has been removed.

It will be immediately recognized that the herein described invention provides a simple, inexpensive means whereby a workman can, without undue efiort, quickly remove the imperfect portion of thread cut into an internal bore. Due to the unique application of the plug base the operation is imparted with a high degree of accuracy to thus remove the danger of harming good thread that is adjacent that being worked.

While the apparatus disclosed and described herein illustrates a preferred form of the invention it should be understood that modifications can be made without deRartin from the spirit of the invention and that modifications t at fa within the scope of the appended claims are intended to be included herein.

What is claimed is:

1. Apparatus for grinding threads of an internally threaded bore comprising:

a. a tool-mounting shaft rotatably disposed within said bore;

b. centering means attached to said tool-mounting shaft for disposing the same in concentric relation to the axis of said bore, said centering means containing external thread means operative to engage the threads of said bore;

. a thread-grinding tool carried by said tool-mounting shaft is axially spaced relation to said centering means, said tool being engageable with the internal thread of said bore and being disposed to translate along a path conforming to the thread helix upon rotation of said mounting shaft.

2. Apparatus as recited in claim 1 wherein said centering means comprises a generally cylindrical body having an external thread about its outer surface and an axial through-opening for receiving the lower end of said mounting shaft and including means for fixedly connecting said mounting shaft to said cylindrical body.

3. Apparatus as recited in claim 2 including means for connecting said thread-grinding tool to said tool-mounting shaft for radially adjustable positioning of said tool with respect to the axis of said shaft.

4. Apparatus as recited in claim 3 wherein said connecting means comprises a tool-support frame comprising:

a. an elongate body disposed in transverse relation to the axis of said mounting shaft;

b. means on said body for attaching said thread-grinding tool;

c. a laterally extending slot disposed in said body;

d. means in said slot for slidably attaching the upper end of said mounting shaft; and

e. means for adjustably moving said body with respect to said mounting shaft. 

1. Apparatus for grinding threads of an internally threaded bore comprising: a. a tool-mounting shaft rotatably disposed within said bore; b. centering means attached to said tool-mounting shaft for disposing the same in concentric relation to the axis of said bore, said centering means containing external thread means operative to engage the threads of said bore; c. a thread-grinding tool carried by said tool-mounting shaft is axially spaced relation to said centering means, said tool being engageable with the internal thread of said bore and being disposed to translate along a path conforming to the thread helix upon rotation of said mounting shaft.
 2. Apparatus as recited in claim 1 wherein said centering means comprises a generally cylindrical body having an external thread about its outer surface and an axial through-opening for receiving the lower end of said mounting shaft and including means for fixedly connecting said mounting shaft to said cylindrical body.
 3. Apparatus as recited in claim 2 including means for connecting said thread-grinding tool to said tool-mounting shaft for radially adjustable positioning of said tool with respect to the axis of said shaft.
 4. Apparatus as recited in claim 3 wherein said connecting means comprises a tool-support frame comprising: a. an elongate body disposed in transverse relation to the axis of said mounting shaft; b. means on said body for attaching said thread-grinding tool; c. a laterally extending slot disposed in said body; d. means in said slot for slidably attaching the upper end of said mounting shaft; and e. means for adjustably moving said body with respect to said mounting shaft. 